The DBA-02 is fast, aggressive, and reasonably well balanced. Their downsides include some of the issues you see, mainly the lack of bass. Well, it's not so much a lack of amount (although there is roll off) and more a matter of lack of thickness. Decay is very short and the note weight simply isn't there. It's short enough in note to even cause the lower midrange to sound a little lean. To get the bass presence you want, you need a thicker note. A thicker note unfortunately means more decay and often a less quick earphone or in some cases a looser, sloppier sound if not simply thick. There's always trade-offs. You just have to decide which you want. For example, the DBA-02 is aggressive and forward, but it's a byproduct of a relatively small dynamic range. You hear a lot because even quiet stuff is reasonably loud. You can get an earphone with more dynamic breadth, but it won't be as forward, and the quiet stuff may be harder to hear unless the earphone has very good clarity and very low distortion.
There's a whole slew of things so we kind of have to start off with a series of questions. You have given us some answers though.
1) You want more bass, or at least more even presence of bass. Since you don't complain about having too much highs or mids, I doubt you are specifically looking for a bass dominant earphone. You likely just want more balance.
2) How much speed and detail are you willing to give up? Does the new earphone need to show you all the tiny little details or would you be willing to step to something a little thicker/smoother?
3) How aggressive do you want the presentation to be? How forward? How in your face? Do you want to have something similar to what the DBA-02 has or would you like something a little less up front for something a little more spacious and ambient?
I will make a note that sound stage on a basic level consists of the room noises (reverberations, reflections, echos). These sounds exist during and more audibly in between the main musical notes. In order to create these in between notes, it is important for the earphone to have a reasonable amount of decay. You need to fill in that time in between. As well, you need a reasonable level of detail and clarity. The clearer the information, the more small bits you can hear. This helps make the space more real, more fleshed out. Dynamics also play a big role in stage space. Loud is close. Quiet is far. Having high dynamic breadth allows an earphone to more correctly portray this range and more fully create a sense of closeness as well as distance. Dynamics add depth. Decay adds thickness and space. Clarity and detail bring out the detail. In this sense an ideal earphone would be one that is very detailed, very accurate, very dynamic, and has a lot of decay, well at least the best mix of these things that is physically possible. If dynamics are less, the presentation becomes a little more forward/close and the depth decreases. If the decay shortens, the stage space begins to lose its realism, becoming almost ghostly or semi-transparent. If the level of detail lacks, the stage space gets more blurry, more vague. If these are bad enough, the earphone pretty much can not create any believable sense of stage space at all, as in you can't really make out any sense of space, distance, location, or separation. Everything is just on top of each other with no real differentiation.. I will say that the DBA-02 is not great in terms of sound stage. It does lack dynamic range and lacks decay. It has speed and detail, but the short decay means that in between detail isn't there at all, even if the driver could play it well if it was.
You bring up the GR07. This is a good earphone. It certainly has a lot better low end than the DBA-02. It is reasonable dynamically, has excellent decay, and is quick. The sound stage is rather good too due to good decay and level of detail. The transparency is also excellent, a testament to very low harmonic distortion as well as minimal mechanical noise. The GR07 is reasonably aggressive but also pretty forgiving. They will show you flaws but not bite your head off.
Because the CK10 can be had within the $250 range, it would also be an obvious suggestion. It will offer you very high speed and detail but also offer you more dynamic range and decay. The low end is much more filled out, but it's still not a bass heavy earphone. It is however well balanced.
The e-Q5 certainly another excellent suggestion. Again like the above two, this is another well balanced earphone, great dynamic breadth, textured. It's energetic but less analytical than the GR07 and doesn't show every little detail like the CK10.
